The constraint made me realize that the complex word isn't that helpful when the other person doesn't know much behind the word. You need to get inventive, and at some point, you might start having fun. I used this to explain encryption, and from the feedback I've got, I seem to have done a good job. It gets repetitive at times, but I managed to slip in PKI, password storage, and a brief summary of the Crypto Wars.
That's pretty well done, actually. Personally, I would add an addendum at the end that breaks out of the ten hundred most commonly used words and actually introduces the reader to the terms you're dancing around.
Thanks. I don't think that having a vocabulary list is necessary. Even though I recall there being such a list at the back of the book, I can't locate it on the XKCD site. I liberally linked to other places to further explain things with the big words. (Isn't that how the web is supposed to work?)
https://theandrewbailey.com/article/177/Hidden-Writing